There are people who are blessed with a remarkable knowledge of vocabulary and diction – people who can come up with beautifully crafted sentences and expressions on most subjects at the drop of a hat. But some times, one tends to go overboard with a desire to show off the abundance of words one has at one's disposal and the result of that might create some confusion for a middling English speaker like me.

Of course, what appears confusing to me may not do so to others. Besides, I believe there is no clear line or distinction between using and overusing one's rich vocabulary. So, this post is not about what you would think showing off one's vocabulary is, but rather what you would call it.

To cut it short, I am looking for a word or phrase to describe

1) someone with an exceptional knowledge of vocabulary and diction
2) using of words and idiomatic expressions by someone in a way that appears to be more a show off and less necessary.

Fustian (also called Fustanum and bombast) is a term for a variety of heavy woven cloth, cotton fabrics, that are chiefly prepared for menswear. It is also used to refer to pompous, inflated or pretentious writing or speech, from at least the time of Shakespeare. This literary use is because the cloth type was often used as padding, hence, the purposeless words are 'bombast'.